For them.
That's the distinction. People are using their own personal experiences and opinions of why the iPad isn't a PC replacement for them, and projecting their needs onto the rest of the user populace. Because god knows everyone needs to code iOS apps, or terminal access, or some other extremely niche use case.
The self-styled pro users here are not a niche group. They are a niche of a niche. To be honest, their computing needs simply aren't representative of the needs of the mass consumer, and they need to stop acting like they are the sole arbiters of what makes a PC and what doesn't.
In the same vein, I don't buy a truck even though there might be that handful of times when I might need to move something. I get a car, and hire movers for the few times I need to transport something bulky.
Your quote stated that according to Phil, some people are indeed using their iPad as their only or primary computer. I fail to see what is wrong with that. Is it so hard to imagine that somewhere out there, there is this individual for whom the iPad meets all his needs, and he doesn't need to go turn on a PC ever?
I will tell you why there is such a huge outburst. These people are afraid. They fear what the future portends. A future where the iPad is the general PC for the masses, and the Mac has been relegated to niche market status. And fear turns to anger and denial.
They cannot stop what is to come.